Industrial gas streams, such as refinery gas streams, natural gas streams, synthesis gas streams, coal gas streams and other such streams generally contain varying amounts of acid gas components. The usual acid gas components are sulfur compounds such as hydrogen sulfide, carbonyl sulfide, carbon disulfide and various alkyl sulfur compounds such as mercaptans. Additionally, carbon dioxide which is considered an acid gas is generally present in such industrial gas streams. Such acid gases are further defined in U.S. Pat. No. 4,094,957, incorporated herein by reference. All of these gas streams are detrimental to the value of the industrial gas stream and in addition, are corrosive to transport equipment and the general environment in which the industrial gases are used. Restrictions have been placed upon the content of acid gas components in industrial gas streams both by the industry and by the government concerned with environmental and atmospheric pollution. Therefore, it has been a long term objective of the industry, to successfully separate and remove acid gas components from the various industrial gas streams in which such components inherently form at least some not insubstantial concentration of the overall gas composition. The prior art has utilized both chemical sorbing materials and physical sorbing materials in efforts to economically remove the acid gas components from industrial gas streams. Alkanolamines have been utilized for the selective removal of acid gas components from various gas streams. Such amines have been utilized with various inorganic components such as inorganic bases for enhanced separation or extraction of acid gas components from gas streams.
The prior art has used various amine compounds for acid gas absorption as in U.S. Pat. No. 1,951,992, but the compounds of that disclosure do not have the tertiary amine and ether linkages of the compounds of the present invention.
In U.S. Pat. No. 2,083,213, hydrogen sulfide is recovered using primary and secondary amines which do not have any ether functionality. Such compounds will operate in a chemical absorption manner with problems of capacity and regeneration.
The prior art has also utilized cyclic nitrogen compounds for the removal of acid gas components from gas streams. In U.S. Pat. No. 3,555,782, morpholine or a C-substituted morpholine is utilized as an acid gas component extraction medium for stripping such components from a gas stream. Specifically, 2-methyl, 2-ethyl, 2-propyl or 2-butyl morpholine are contemplated for acid gas removal. Non-alkyl substituents may also be utilized such as 2-ketomorpholine. However, it is stated that N-substituted morpholines are not particularly effective for the purpose of the invention.
In U.S. Pat. No. 3,516,793, alkanolamines or morpholines are used in conjunction with the monoalkyl ether of a polyhydric alcohol to absorb hydrogen sulfide from a gas stream. Morpholine is preferred to the substituted forms, such as morpholine ethanol, morpholine ethanol ethyl ether and morpholine phenyl.
U.S. Pat. No. 4,094,957 discloses various tertiary amines used in the treatment of acid gases as activators for chemical absorbents of alkali salts and hydroxides. Combinations of tertiary amine and ether functionality are not set forth.
The hydrolysis of acid components such as carbonyl sulfide are known to be catalyzed by piperazinone and alkyl-substituted piperazinones as set forth in U.S. Pat. No. 4,100,256.
Selective extraction of hydrogen sulfide and lower alkyl mercaptans with piperazinone or alkyl-substituted piperazinone is also known in the prior art as suggested by U.S. Pat. No. 4,112,049. This patent recites that additionally alkanolamines and morpholine derivatives, such as N-methyl-3-morpholinone are known sour gas purification solvents.
The use of morpholines and piperazines as hydrolysis catalysts for carbonyl sulfide is also set forth in European patent application No. 0 008 449.